Exemplary embodiments herein relate to motor vehicle supplemental restraint systems, and more particularly, to a multi-chamber knee airbag for protecting an occupant from colliding with an object such as an interior panel in front of a seat in the event of a vehicle collision.
Vehicles generally provide some kind of supplemental restraint system. Often, these supplemental restraint systems take the form of inflatable devices or restraints. In some cases, an inflatable restraint system includes a leg protection device having an airbag deployed in front of the vehicle occupant to receive the legs of the occupant in the event of a vehicle collision so as to protect the vehicle occupant.
In one known leg protection device, a single chamber is formed inside the airbag. The occupant sitting on a vehicle seat may assume various sitting postures, for example, with knees apart and/or with legs extending sideways. The positions of the knees may be often spaced apart from a center of the seat. Therefore, the airbag of the leg protection device is designed to rapidly spread in the vehicle lateral direction after start of inflation. Having a single chamber, a dimension of the inflated airbag in a vehicle longitudinal direction (hereinafter, sometimes referred to as a thickness of an airbag) tends to be large. Therefore, sufficient inflation of the airbag can provide a large thickness for receiving the occupant's legs. However, if the airbag is designed to expand laterally as well, the inflation volume can become so large that a gas generator or inflator having a significantly large generating capacity is required.
In another known leg protection device, the airbag includes multiple chambers which are separated by partitions formed inside the airbag. The partitions have through ports or holes for the gas to flow between the chambers. Since the multi-chamber airbag has a relatively large volume, the gas generator is required to have a large capacity to quickly inflate the chambers located on a periphery of the airbag, resulting in relatively poor gas efficiency. Further, it can be difficult to control stiffness of different sections of the known airbag for different sized occupants.